A recoilless weapon, typically, comprise a launch tube or barrel, open at muzzle and breech ends thereof, a projectile in the middle part of the launch tube and a counter mass in the rear part of the launch tube. Between the projectile and the counter mass is a propellant disposed, which propellant upon activation, causes the projectile and the counter mass to expel out from the launch tube. Main characteristics are; low recoil-force, low air-pressure and low heat-signature. Low recoil forces and low pressures are of particular importance when a weapon is fired from a gunners shoulder in confined spaces, such as in small rooms or bunkers.
Currently, few recoilless weapons exist, which fulfils requirements for safe use in confined spaces, which weapons are small and compact for easy handling and still acceptable in firing range.
New countermasses have been developed to reduce recoil, pressure and heat-signature. Countermasses comprising liquids for extinguishing of flames, countermasses based on compacted powders for rapid decomposition and segmented countermass adapted to release sequentially.
Much work has also been devoted to the internal ballistics of a counterless weapon. New high- and low pressure systems with improved balance between a projectile and a countermass, such that recoil and air pressure are reduced.
WO 03/064956 discloses a counterless weapon with a high- and low pressure system. The high- and low pressure system is arranged in the launch tube behind the projectile. The high-pressure part is constituted by a propellant chamber, partly filled with a propellant, and the low pressure part is constituted by a countermass chamber, partly filled with a countermass, behind the propellant chamber. Between the high pressure part and the low pressure part is gas-openings arranged. The gas openings provide a gas passage between the high pressure part and the low pressure part.
A problem, however, with the high- and low pressure system in WO 03/064956, is that the gas pressure in the low pressure part may increase too fast if the gas passage is large. Fast increase of the gas pressure causes a quick and early expelling of the countermass. Early expelling of the counter mass may have an adverse effect on recoil and pressure, especially, if the propellant is subjected to heat, since heat increase the burning-rate of the propellant. The gas-passage may be restricted by reducing the cross-flow area of the gas openings. On the other hand, if the gas-passage is restricted, the gas-pressure may increases too slow, causing late expelling of the countermass. Late expelling may have an adverse effect on the firing range of the weapon. Too fast or too slow expelling of the counter mass has an adverse effect on the inner-ballistic properties of the weapon.
Accordingly, there is a need for a high- and low pressure system with improved balance between the projectile and the counter-mass such that recoil force and air pressure are kept low, while firing range high still are acceptable.
A further problem, related to the arrangement with a high- and low pressure system in the launch tube, is that the launch tube tends to be long and ungainly.